Selective bird feeders are known in the art and are designed to limit the maximum size of a bird or animal which can access the seed in the feeder. The reasons for excluding certain birds may be many. Thus, as disclosed in U.S. Pat. No. 3,241,525, there is provided a selective bird feeder which is specific to cardinals. As taught by this patent, a favorite seed of cardinals is the sunflower seed; this seed is also popular with both smaller and larger birds.
Some larger birds will also attempt to access the seed and some such birds including crows, grackles, bluejays and the like are considered by some people to be undesirable.
A further problem associated with bird feeders are marauders which gain access to the seeds. In particular, squirrels are well known for their ability to reach the seed in a bird feeder and to devour the same. Many approaches have been tried to discourage or prevent squirrels from reaching the bird feeder, including various types of covers and baffles on poles. These seldom work as the squirrels have shown great ingenuity in overcoming such devices.
The prior art also teaches other solutions to the problem utilizing shrouds. These may be exemplified by U.S. Pat. No. 4,646,686 to Furlani which teaches a moveable shroud. Other shroud-type squirrel resistant bird feeders are those such as shown in U.S. Pat. Nos. 6,253,707 and 6,543,384.